Explosive lines

ABSTRACT

An explosive line including a pliable impervious outer casing and a filling of explosive material within the casing. An outer surface of the casing has a plurality of generally flat faces which are spaced about the explosive line so as to provide an outer surface of generally polygonal section.

BACKGROUND OF THE INVENTION

This invention relates to explosive lines sometimes known as detonationcord.

A standard form of explosive line is a small diameter water imperviouspliable plastic casing or tube containing an explosive charge. Suchexplosive lines are commonly and extensively used in demolition work,for example, and are also utilised in some forms of minefield breachingsystems in which they are adapted to be carried by means of a projectileacross a minefield, whereafter they are detonated to breach a pathwaythrough the minefield.

Commonly, such explosive lines are packed ready for use within acontainer of circular plan view, the line being carefully wound withinthe container so that it can, after removal of the lid of the container,be easily and smoothly withdrawn therefrom to any required length.

It is an object of the present invention to provide an improvedexplosive line.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided an explosive linecomprising a pliable impervious outer casing and a filling of explosivematerial, the casing being such that the outer surface thereof has aplurality of generally flat faces. The generally flat faces may bespaced about the explosive line so as to provide an outer surface ofgenerally polygonal section such as triangular, rectangular or square,for example.

The casing is preferably of an appropriate plastics material, or a wovenor knitted natural or artificial fibre for example.

To ensure that the explosive line encloses maximum mass and volume ofexplosive, the inner surface preferably generally follows the outersurface in its configuration.

Previously available explosive line has been of a generally circularform in cross-section, which has meant that when coiled and layeredwithin a container therefor ready for use, of necessity a multiplicityof unused spaces are present between and around the coiled explosiveline. By means of the invention, it is possible to ensure, by arrangingto abut appropriate generally flat faces of the outer surface of theexplosive line against one another, that the line can fit more closelywithin the container, with few, if any, spaces between successive coilsand layers. The result of this is either that within a given sizecontainer, a greater volume of line can be accommodated, or (and perhapsmore usefully) the same volume of explosive line can be fitted within acontainer of smaller dimensions and therefore lesser weight. Thisreduction in weight is clearly advantageous in general terms, but isparticularly so in relation to the use of an explosive line in minefieldbreaching systems, since it reduces the substantial weight which aninfantry soldier carrying such a minefield breaching system has tocarry.

It is to be understood that the expression "generally flat faces" inrelation to the explosive line and in the context of a pliable casingincludes faces of some limited curvature, subject to satisfying theintent that reduction of packing space is provided by abutting generallyflat faces against one another.

As has been specified hereinabove the configuration of the explosiveline in accordance with the invention can be a three or four sidedfigure, but it is to be noted that the configuration can be such as tohave even a greater number of generally flat sides, such as from five toten flat sides. By providing such a configuration, in addition to thepossibility of accommodation space reduction hereinbefore mentioned,study of the literature shows that with appropriate design a maintainedor even increased explosive effect can be produced at the same time asthe geometric size and/or weight of the explosive line has been reduced.The practical effect of this is that not only can the line be used forminefield breaching for example as hereinabove described, but also canbe used for the breaching of obstacles, such as barbed wire, because ofthe possibility of increased explosive effect.

The plurality of generally flat sides may include at least some whichare re-entrant so as to provide what can best be described as a"concave" portion to the explosive line. This provides the explosiveline on at least some sides with a hollow shaped charge structure. Ifsuch re-entrant sides are spaced all around the explosive line, inpractice effectively a hollow charge structure will always be facing atarget, in the sense of mine clearance or obstacle breaking, of theexplosive charge. Such hollow shaped charges are known to provideheightened explosive effects, by what is known as the "Munroe effect" orthe "cavity effect". By increasing the explosive effects still further,such re-entrant sides, most importantly for the present invention,enable the reduction of the total weight of the explosive line per unitvolume of line considerably.

The re-entrant walls of the explosive contained within the line may belined with a coating of a non-explosive material such as paper or ametal such as copper, aluminium, tungsten or any other appropriatemetal. Such a lining acts as an energy carrier and concentrator. Themetal or similar material may be added as a foil coating to theexplosive before applying the pliable impervious outer casing of theexplosive line of the invention.

The use of the just mentioned geometrical configuration of the explosiveline can significantly reduce the size and weight of a man portableminefield and/or obstacle breaching kit.

In one preferred embodiment of the invention, the explosive line may beof star configuration with, for example, five points to the star therebyhaving ten re-entrant generally flat surfaces. Such star shaped lineallows very tight packing density in a portable container compared withthe circular section configuration of explosive line previously used,which is a most useful practical result.

The charge may be provided with a hollow portion along its length, whichmay be along the centre of the charge or offset to one side. Such anarrangement can reduce the weight per unit volume of the line withoutreducing the explosive effectiveness.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood, twoembodiments thereof will now be described by way of example withreference to the accompanying drawings in which:

FIG. 1 is an isometric view of a rectangular shaped length of explosiveline in accordance with the invention;

FIG. 2 is a cross-section on an enlarged scale of the explosive line ofFIG. 1;

FIG. 3 is a cross-section of a square section explosive line inaccordance with the invention; and

FIG. 4 is a cross-section of a five pointed star section explosive linein accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1 and 2 it will be seen that the explosive line 1comprises a flexible and pliable casing 2 of appropriate imperviousplastics material of rectangular configuration both on its outer andinner surfaces, and having two opposed larger flat sides 3, 4, and twoopposed smaller flat sides 5, 6.

The arrangement of FIG. 3 is similar except that in this case all foursides 7, 8, 9, 10 of the casing 11 are of equal dimension.

In each example, the explosive line is provided with a continuous lengthof explosive material 12.

The explosive lines of the embodiments of FIGS. 1 and 2 can be fittedwithin an open-topped container of circular plan very tightly byappropriate coiling and layering leaving practically no spaces betweencoils and layers of an explosive line wound therein, so that a givenquantity of explosive line can be fitted into a smaller and hencelighter container than if the explosive line were of circular section.

Reference to FIG. 4 illustrates another embodiment of the invention inwhich the explosive line 15 comprises an extrusion of an imperviousplastics casing 16 having ten re-entrant flat outer surfaces 17 andcorresponding inner surfaces 22 forming an explosive line of fivepointed star configuration within which is disposed an appropriateexplosive charge 18. As can be seen the charge is provided with a hollow19 along its length about its centre.

As previously mentioned the use of the hollow shaped charge provided bythe re-entrant sides produces, by the Munroe effect, an increasedeffectiveness in operation of the explosive charge. At the same time,and most significantly, as can be seen by the part of an adjacentexplosive line 20 of five pointed star shaped indicated in dotted lines,it is possible for the star shaped line to be very closely packedcompared to a circular section explosive line 21 having the same maximumdiameter as the star shaped line, so that packing volume in a portablecontainer is most substantially reduced, whilst at the same time theweight per unit length of the explosive line is significantly reduced,both of which effects are of extremely considerable benefit to theoperator carrying the container with a normal operational length ofexplosive line.

It is to be understood that the foregoing is merely exemplary ofexplosive lines in accordance with the invention and that modificationscan readily be made thereto without departing from the true scope of theinvention.

What is claimed is:
 1. An explosive line comprising a pliable imperviousouter casing and a filling of explosive material within the casing, thecasing being such that the outer surface thereof has a plurality ofgenerally flat faces, and the explosive material within the casingincluding an internal hollow shaping along its length, said hollowshaping being surrounded entirely by said explosive material.
 2. Anexplosive line as claimed in claim 1 wherein the generally flat facesare spaced about the explosive line so as to provide an outer surface ofgenerally polygonal section.
 3. An explosive line as claimed in claim 1wherein the casing is formed of a plastics material.
 4. An explosiveline as claimed in claim 1 wherein the inner surface of the outer casinggenerally follows the outer surface in its configuration.
 5. Anexplosive line as claimed in claim 1 wherein the configuration of theouter surface has ten generally flat sides.
 6. An explosive line asclaimed in claim 1 wherein the plurality of generally flat sidesincludes at least some which are re-entrant so as to provide, in effect,a concave portion to the line.
 7. An explosive line as claimed in claim6 wherein the re-entrant sides are spaced around the line.
 8. Anexplosive line as claimed in claim 7 of star configuration.